CN116096665A

CN116096665A - Improvements in or relating to stairlifts

Info

Publication number: CN116096665A
Application number: CN202180046981.1A
Authority: CN
Inventors: 马克斯·丹尼尔·伍德汉姆斯; 安德里亚斯·乔鲍·圣迪斯特万尼
Original assignee: Stannah Stairlifts Ltd
Current assignee: Stannah Stairlifts Ltd
Priority date: 2020-06-30
Filing date: 2021-06-29
Publication date: 2023-05-09
Also published as: WO2022003332A1; US20230249944A1; GB202109320D0; EP4172095A1; GB2598657A; GB202010021D0

Abstract

The present invention relates to a friction driven stairlift having a pair of drive wheels in frictional engagement with an upper surface of a stairlift rail, the drive wheels being mounted for rotation in a vertical plane passing through a centerline of the stairlift rail. The track is preferably formed of two substantially parallel tubes, the carriage being held perpendicular to the portion of the track that it contacts at any given time.

Description

Improvements in or relating to stairlifts

Technical Field

The present invention relates to stairlifts and in particular, although not necessarily exclusively, to a stairlift in which the stairlift track includes a change in inclination and/or direction. Such stairlifts are commonly referred to as curved stairlifts and are in contrast to straight stairlifts, in which the track is at a single, fixed angle of inclination.

Background

Many forms of curved stairlifts are available today to meet the needs and wishes of the user in a number of ways. In general, people have increasing demands not only for functions but also for convenience in manufacturing, installation and maintenance; and there are increasing demands on ride quality and aesthetics. Most desirably, the stairlift has a section at the lower end of the rail that is vertical to allow the carriage to travel downwardly to a position where the foot rest is positioned near the ground for safe installation and removal of the stairlift. Furthermore, a steep horizontal curve at the curve of the track is required in order to minimize the intrusion of the track into the stairs.

Most stairlifts currently available include rack and pinion drives. Such a drive is robust and reliable, but has certain limitations in use. For example, the track sections must be provided with a length that is a multiple of the rack pitch, and when the track sections are joined together, the pitch is not always exactly matched. Thus, the ride quality is affected, but in any event the rack and pinion drive is not optimal; and this problem increases with increasing carriage speed. In view of the desire to keep the speed of the stairlift as high as possible at the maximum allowed 0.15m/sec, the ride quality problem is a significant drawback of rack and pinion drive. Furthermore, there is a limit to the bending radius that can be accommodated, since the pitch and/or alignment changes at the bend and may to some extent lead to problems with the engagement of the drive pinion.

Friction drives have been proposed as an alternative to rack and pinion drives. U.S. patent No.2,888,099 describes a friction driven stairlift in which a plurality of drive wheels on a common drive shaft line are biased into contact with the top plate of an angular section rail. In order to keep the axis of the carriage vertical and to keep the chair horizontal through transitional bending, the relative rotation between the chair and the carriage is achieved by means of mechanical links acting on leveling bars fixed to the rail and extending along the rail, below the top plate of the rail. This limits the steepness of the track angle that can be achieved and, although disclosed in the patent text, the described stairlift may be configured to include a bend in the horizontal plane (also referred to as an inner/outer bend), this type of bend is not described or illustrated and, due to the wide width of the track section and the drive wheels, any horizontal bend must have a large radius, making the stairlift unsuitable for installation on a stairlift of a domestic dwelling.

Another form of friction driven stairlift is described in GB 2 379 209 to the applicant. In this patent the track is formed by two vertically spaced tubes, on which the carriage of the stairlift is slidably mounted by means of so-called pulleys. The carriage also includes a support roller that abuts the down tube to prevent the carriage and chair assembly from tilting forward or rotating about the longitudinal axis of the track. Since the carriage remains always vertical, there is a limit to the track angle that can be adapted, since at steeper track angles the lower support roller is less and less in contact with the bottom track tube, such as the track arrangements described in published international patent applications WO 2005/085114 and WO 2017/187161 cannot be achieved, since the lower support roller will not be in contact with the bottom track tube at all. Another problem with the stairlift described in this patent is that in the inside/outside bending the drive roller will cross the surface of the upper tube laterally, resulting in increased wear.

Another friction drive stairlift arrangement is described in published international patent application WO 2014/098573. A rail is provided that is cylindrical or oval in cross-section with opposite sides inwardly forming laterally facing recesses that extend the length of the rail. The drive wheel is located within the recess. The described device is considered to have some limitations. First, the cross-sectional shape of the rail is difficult to form, particularly difficult to form so that the cross-sectional shape is maintained in bending. Another problem is that, since the drive wheel is engaged in a recess in the rail-side surface, the carriage must have a sufficient width to accommodate the drive means. The drive itself limits the radius of the inside/outside bending that can be achieved, while the lateral bulk of the device also limits the track-to-wall size that can be achieved. Finally, the drive wheel must not only provide friction to drive the carriage along the track, but must also react to loads that tend to cause the carriage to tilt or roll about the track axis. Thus, it is expected that the drive wheel will experience considerable wear.

The object of the present invention is to provide a friction-driven stairlift which solves the above-mentioned problems at least to some extent; or at least may provide a novel and useful choice.

Disclosure of Invention

Accordingly, in a first aspect, the present invention provides a stairlift comprising a rail having a top surface and a length-wise axis extending parallel to the top surface; a carriage mounted on the track for movement therealong, the carriage and the track being configured such that the carriage is substantially perpendicular to the lengthwise axis at any location on the track; and a chair mounted on the carriage, wherein the top surface defines a drive surface extending along the track, the carriage including a plurality of drive rollers configured and arranged to frictionally engage the drive surface at spaced locations on the drive surface, a reference plane passing through a center of each drive roller, perpendicular to a rotational axis of each drive roller, through a center line of the track at any location of the carriage on the track, the carriage further including biasing means for biasing the drive rollers against the drive surface; and means for resisting rotational movement of the carriage about the lengthwise axis.

Preferably, the drive surface is defined by a first longitudinally extending member, the means for resisting rotational movement of the carriage about the lengthwise axis is defined in part by a second longitudinally extending reaction surface, and wherein the reaction surface is spaced from and below the drive surface when the track is in its use position.

Preferably, the first and second longitudinally extending members comprise two substantially evenly spaced tubes of circular cross section which are arranged substantially one above the other when the track is mounted for use.

Preferably, the drive roller engages an upper tube of the two spaced tubes, and the biasing means comprises one or more biasing rollers engaging a bottom surface of the upper tube.

Alternatively, the drive roller engages an upper tube of the two spaced tubes and the biasing means comprises one or more biasing rollers engaging a lower tube of the two spaced tubes.

Preferably, the biasing roller defines in part the means for resisting rotation of the carriage about the lengthwise axis.

Preferably, the means for resisting rotational movement of the carriage about the longitudinal axis comprises a plurality of support rollers engaged with a lower tube of the two spaced tubes.

Preferably, the plurality of support rollers comprises two rollers engaging the lower tube on opposite sides of a longitudinal centerline of the lower tube.

Preferably, the two rollers comprise a first roller rotatable about a fixed axis; and a second roller rotatably mounted on an arm mounted for pivoting about the fixed axis.

Preferably, the biasing roller is mounted and configured to apply a biasing force along a spaced apart biasing axis that is substantially perpendicular to the lengthwise axis.

Preferably, the drive rollers are mounted for pivoting about pivots perpendicular to the lengthwise axis, each of the pivots lying in a reference plane of the respective drive roller.

Preferably, the contact surface of the drive roller has substantially the same shape as those portions of the track with which it is in contact when viewed along the lengthwise axis.

Preferably, the stairlift further comprises a levelling facility configured and operable to effect relative rotation between the chair and the carriage to maintain the chair substantially horizontal as the carriage moves through the curvature of the rail in a vertical plane.

Preferably, the track comprises a bend having a bend radius substantially equal to twice the diameter of the tube forming the tail when viewed from above.

Preferably, the drive roller has a drive surface formed of polyurethane having a shore hardness (shore hardness) in the range of 92 to 95.

Preferably, the stairlift, when mounted in a stairlift, the rail has an upper end and a lower end, the portion of the rail terminating at the lower end being substantially vertical.

Many variations of the embodiments of the present invention will appear to those skilled in the art. The following description is merely illustrative of one method of practicing the invention, and variations or equivalents are not described in a manner that is not to be considered limiting. Within the scope of the appended claims, the description of a particular element should be construed as including any and all equivalents thereof, whenever possible, whether present or not in the future.

Drawings

The invention will now be described with reference to the accompanying drawings, in which:

fig. 1: an isometric view of a portion of one example of a stairlift embodying the invention is shown;

fig. 2: an enlarged isometric view of a base chassis component within the stairlift carriage of fig. 1 is shown;

fig. 3: an enlarged partial cutaway isometric view of the carriage and rail of fig. 1 is shown;

fig. 4: an isometric view from the rear of a portion of an upper roller assembly contained in the carriage of fig. 3 is shown;

fig. 5: a front isometric view of the carriage of fig. 3 and 4 is shown illustrating the lower roller assembly;

fig. 6: an isometric view of the carriage configuration through the inner bend is shown;

fig. 7: what is shown from above in fig. 6 is shown, with parts omitted for clarity;

fig. 8: an isometric view of the carriage described previously from above through an external bend is shown;

fig. 9: a top view of the carriage described above when bent through a negative transition is shown;

fig. 10: a view similar to that of fig. 9 is shown but from the rear;

fig. 11: a view similar to that of fig. 10 is shown, but with the carriage bent through a positive transition;

fig. 12: an isometric view of a portion of a stairlift embodying a second form of the invention is shown;

fig. 13: a partial cross-sectional view of a portion of the stair lift carriage of fig. 12 along the rail axis is shown;

fig. 14: an isometric view of the carriage shown in fig. 12 and 13 from the front is shown;

fig. 15: a top view from the front of the carriage of fig. 12-14 through a positive transitional bend is shown;

fig. 16: a view similar to fig. 15 is shown, but with the carriage bent through a negative transition;

fig. 17: an isometric view from the rear of the carriage of figures 12 to 16 is shown as it passes over the outer curve; and

fig. 18: an isometric view from the rear of the carriage of figures 15 to 17 is shown as it passes through the inner curve.

Detailed Description

Referring first to fig. 1, a first embodiment of a stairlift 100 is shown that includes a carriage 101 mounted on a rail 102 for movement along the rail. In a conventional manner, the carriage is fitted with an interface (not shown) through the frame 103, which in turn mounts a chair (not shown). A leveling mechanism (not shown) is provided to effect relative rotation between the interface and the carriage so that the chair remains substantially horizontal throughout the movement of the carriage along the track. Suitable forms of leveling apparatus are well known to those skilled in the art and will not be described in this disclosure as such are not inherent to the present invention.

The rail 102 has a drive surface and a surface positioned and configured to inhibit rotation of the carriage about a longitudinal axis of the rail. In this embodiment, the drive surface is provided by the upper surface of the rail, in this case the top surface of the upper tube of the rail comprising spaced apart upper and

lower tubes

104, 105. The surface positioned and configured to resist rotation of the carriage about the longitudinal axis of the rail is conveniently provided by a side surface of the down tube 105. In a known manner, the

tubes

104 and 105 are preferably formed of circular cross-section metal tubes, which are vertically spaced apart and maintained at a substantially constant spacing by a C-shaped bracket 106. A non-limiting example of a suitable tube is a low carbon steel round section tube with a nominal outer diameter of 45mm.

As shown in fig. 1, the track includes a negative transition curve 107, a positive transition curve 108, an outer curve 109, and an inner curve 110. Also shown in fig. 1 is a lengthwise axis 111 that follows the direction and angle of the various portions comprising the track.

The carriage and rail are configured such that the carriage axis 112 (fig. 5) remains perpendicular to the direction or longitudinal axis 111 of the rail, regardless of the position of the carriage 103 on the rail 102, which carriage axis 112 is vertical when the carriage traverses the rail of the horizontal portion. This is achieved by arranging the

track pipes

104 and 105 at a substantially constant vertical spacing, and by the configuration of drive rollers and biasing means as will be described in more detail below.

In the present embodiment, the carriage 101 includes a drive roller assembly 113, which drive roller assembly 113 is configured to frictionally engage the upper rail tube 104, and in particular, a drive surface in the upper surface of the upper rail tube 104. As shown, the drive roller assembly 113 includes a pair of friction rollers 116 that engage spaced points on the drive surface; and a biasing device, in this case a pair of biasing rollers 118, which engage the lower surface of the upper rail tube 104 and which are configured, mounted and positioned to bias the friction rollers 116 into contact with the upper rail tube 104. The drive rollers and the bias rollers are preferably provided in groups, one of which 119 is shown in fig. 4. In the present embodiment, each group 119 further includes a drive motor/gear box unit 120 for providing a driving force to the drive roller 116. Each drive roller 116 is mounted for rotation in a bracket 121, the bracket 121 comprising laterally extending projections 122 on both sides, the projections 122 comprising apertures 123, the apertures 123 receiving shafts 125 extending upwardly from a bracket 126 parallel to the carriage axis 112, the bias rollers 118 being rotatably mounted in the bracket 126. An upper cross member 127 is secured to the upper end of the shaft 125, and a biasing member such as a coil spring 128 is conveniently disposed about the shaft 125 and acts between the projection 122 and the cross member 127 to displace the biasing roller 118 toward its respective drive roller 116. However, those skilled in the art will appreciate that other means may be provided to apply the bias, including pneumatic and/or hydraulic means.

Two roller sets 119 are mounted on the chassis base member 130, as shown in fig. 2. Pins or the like (not shown) pass through spaced mounting holes 131 in the chassis cross member 132 and engage mounting holes 133 in the drive roller bracket 121. This allows each roller set 119 to pivot about a mounting axis 134, as shown in fig. 7. When the carriage is mounted to the rail, the axis 134 passes through the longitudinal centerline of the upper rail tube 104 and is parallel to the carriage axis 112.

The second roller assembly 114 preferably comprises a pair of rollers that engage the lower track tube 105 on opposite sides of a vertical axis passing through the centerline of the tube 105. As shown, the roller assembly 114 is mounted on a shaft 136 aligned parallel to the carriage axis 112, the shaft 136 being located within a bore 138 of the chassis base. The pair of rollers includes a main reaction roller 140 freely rotatable on a fixed axis defined by the shaft 136, and a positioning roller 142 rotatably mounted on an arm 143 projecting from the lower end of the shaft such that the arm is pivotable about an axis 144 of the shaft. The axle 136 may also be raised and lowered within the chassis base, as indicated by arrow 145 in fig. 3. This allows the carriage to accommodate any variation in the spacing of the

rail tubes

104 and 105 as it travels along the rail, such as typically occurs in transitional bends; but also due to variations in manufacturing tolerances. It can be seen that the axis 144 of the shaft is located midway between the axes 133 when the carriage is seen from a front or rear view.

Fig. 8 shows the behavior of the roller assembly as it passes through an outer bend. It can be seen that the roller set 119 of the upper roller assembly pivots about axis 134 in a first but opposite manner. The roller set is shown as being inwardly curved in fig. 6 and 7, it being seen that the roller set 119 again pivots about axis 134 but in a second opposite manner. It will also be appreciated that in both the inner and outer bends, the arm 143 mounting the registration roller 142 can pivot about the axis 144 to maintain the reaction roller and registration roller in contact with the lower track tube 105.

Fig. 9 and 10 show the behavior of the roller set when bending through a negative transition from the front and from the rear, respectively, while fig. 11 shows the behavior of the roller set when bending through a positive transition from the rear. When bent by both types of transitions, the biasing roller 118 is displaced relative to the drive roller 116 in a direction parallel to the carriage axis 112 as indicated by arrow 146 in fig. 10, with the shaft 125 sliding in the bore 123 under the bias of the spring 128. The second or lower set of rollers can also be moved in the direction of arrow 145 in fig. 3 to accommodate any change in track pitch in the transitional bend.

Turning now to fig. 12-18, a second example of a stairlift 200 embodying the invention is shown. As shown in fig. 12, the stairlift 200 includes a carriage 201 mounted on a rail 202 for movement along the rail. In a conventional manner, the carriage mounts an interface (not shown) on the front surface 203 of the carriage chassis 204, which in turn mounts a chair (not shown). A leveling mechanism (not shown) is provided to effect relative rotation between the interface and the carriage so that the chair remains substantially horizontal throughout the movement of the carriage along the track. As mentioned above, leveling facilities are not inherent to the present invention and will not be further described in this disclosure.

As with the previously described embodiments, the track 202 has a drive surface and a surface positioned and configured to resist rotation about the longitudinal axis of the track. As with the previously described embodiments, the drive surface is defined by the top surface of the upper rail tube 205, while the reaction surface is preferably provided by the side surface of the lower rail tube 206. The

rail tubes

205 and 206 are preferably vertically spaced and maintained at a substantially constant vertical spacing by brackets 207, the brackets 207 preferably being aligned along, or substantially along, the longitudinal centerline of the

rail tubes

205 and 206.

As shown, the track includes a negative transition curve 208, a positive transition curve 209, an outer curve 210, and an inner curve 211. Also shown is a lengthwise axis 212 that follows the direction and angle of the various portions comprising track 202.

The carriage is configured such that, regardless of the position of the carriage 203 on the track 202, the carriage axis 215 (fig. 14) remains substantially perpendicular to the track's direction or length axis 212, which carriage axis 215 is vertical when the carriage is travelling on a horizontal portion of the track. This is by a constant spacing of the track pipes and providing the carriage with a first or upper set of rollers 213 that engage the upper track 205 and a biasing means 214 that engages the lower track 206, and the biasing means 214 operates to engage the upper set of rollers with a drive surface on the upper track 205.

In this embodiment, the first roller assembly 213 is configured as a set of drive rollers and is further configured to frictionally engage with spaced points on the upper surface portion of the upper rail tube 205. As shown, the upper roller assembly 213 includes a pair of friction drive rollers 216 mounted in an inverted U-shaped bracket 218 for rotation about an axis 219. The brackets 218 are mounted on the chassis base 204 to pivot about spaced axes 220, the axes 220 being parallel to the carriage axis 212 and passing through the longitudinal centerline of the upper rail tube 205. A motor/gear box unit (not shown) is preferably mounted on a bracket 218 to provide the driving force to the roller 216, the bracket also mounting a support roller 222 on the free end of the U-arm, the roller 222 acting to maintain the drive roller 216 in proper alignment with the upper track tube 205 and to resist lateral loading of the roller 216.

In the first embodiment described above, both the drive roller and the biasing means required to maintain the drive roller in engagement with the rail are engaged with the upper rail tube. In this second embodiment, the drive roller still drives the upper rail tube 205 while applying a biasing force to the lower rail tube 206. In this embodiment, the biasing means is conveniently provided by a second or lower roller assembly 214 comprising a biasing roller 225, the biasing roller 225 being configured and positioned to apply an upward biasing force along the longitudinal centerline of the lower track pipe 206. The assembly 214 also includes a pair of

registration rollers

226 and 227 positioned to engage the lower track tube 206 on opposite sides of a longitudinal centerline through the lower track tube 206 and configured to resist lateral movement of the roller set 214 in or substantially in the horizontal centerline direction of the lower track tube 206.

Rollers

225, 226 and 227 are mounted in a bracket 230, which in turn is mounted on a lower bracket 232 for pivotal movement about axis 233; the axis 233 is parallel to the carriage axis 215. Roller 227 rotates about axis 233, while roller 226 is rotatably mounted on a bracket at a location spaced from axis 233, bracket 230 effectively comprising an arm that pivots about axis 233.

The lower bracket 232 is mounted on the carriage chassis 204 for sliding movement in the direction of arrow 234 (fig. 14). Likewise, movement in the direction of arrow 234 is also parallel to carriage axis 215, with the axis of movement being substantially midway along axis 220. In the illustrated form, two posts 235 extend upwardly from the lower bracket 232 and are slidably received in holes 236 formed in an upper surface 237 of the carriage chassis 204. A compression spring 238 is preferably provided, mounted around the post 235, and acting between the post and a circlip 239 mounted in a base 240 of the carriage chassis 204 to bias the biasing roller 225 vertically upward on the lower track tube 206.

Fig. 15 and 16 show the characteristics of

roller assemblies

213 and 214, respectively, from the front side as they bend through a negative transition. When flexed by both types of transitions, the lower roller assembly 214 is displaced relative to the upper roller assembly in a direction parallel to the carriage axis 212, as indicated by arrow 234, to resist the bias of the compression spring 238. This not only enables the carriage to pass through the transitional bend, but also accommodates any change in rail tube spacing, whether or not such change occurs at the transitional bend. In fact, although the spacing between the rail tubes is substantially constant, some variation may be deliberately introduced in order to maintain the biasing force exerted by the lower roller assembly substantially constant.

Fig. 17 shows the behavior of the roller assembly when passing through an outer bend from the rear. It can be seen that the drive roller 216 pivots about the axis 220 in a first opposite manner to accommodate bending. Fig. 18 shows the behavior of the roller 216 in an inner bending from the rear, it being seen that the roller again pivots about the axis 220, but in a second opposite manner to that shown in fig. 17. It can also be seen that in both the inner and outer bends, the bracket 230 mounting the lower roller set 214 can pivot about an axis 233 to maintain the lower roller assembly in contact with the lower track tube 206.

In both embodiments described, the drive roller is preferably formed of a high friction plastic material, such as polyurethane, although this is not required and any suitable material may be used. It has been found that polyurethane drive rollers having a shore hardness of between 92 and 95 are particularly suitable. Lower hardness materials can be used to provide more friction but at the cost of a greater wear rate. Also, a harder material will exhibit less wear, but provide less friction.

The use of two small friction drive wheels, typically but not limited to 75-100mm in diameter at the center, allows the stairlift to exhibit better ride quality than rack and pinion drive systems, and also allows for accommodating steeper bends and steeper track angles. Depending on the geometry of the sledge, it is envisaged that an inner bend of substantially 2 times the nominal tube diameter may be achieved, which means that an inner bend of radius 90-100mm formed by a tube of nominal diameter 45mm may be adapted. This in turn allows for improved engagement of the track with the stairs.

Claims

1. A stairlift comprising a rail having a top surface and a lengthwise axis extending parallel to the top surface; a carriage mounted on the rail for movement therealong, the carriage and the rail being configured such that the carriage is substantially perpendicular to the lengthwise axis at any location on the rail; and a chair mounted on the carriage, wherein:

the top surface defining a drive surface extending along the track, the carriage including a plurality of drive rollers configured and arranged to frictionally engage the drive surface at spaced locations on the drive surface, a reference plane passing through a center of each drive roller, perpendicular to a rotational axis of each drive roller, through a centerline of the track at any location of the carriage on the track, the carriage further including biasing means for applying an effective clamping bias to clamp the drive rollers on the track; and means for resisting rotational movement of the carriage about the lengthwise axis.

2. A stairlift as claimed in claim 1 wherein said drive surface is defined by a first longitudinally extending member, said means for resisting rotational movement of said carriage about said lengthwise axis being defined in part by a second longitudinally extending reaction surface, and wherein said reaction surface is spaced from and below said drive surface when said rail is in its use position.

3. A stairlift as claimed in claim 2 wherein said first and second longitudinally extending members include two substantially evenly spaced circular cross-section tubes arranged substantially one above the other when the rail is in use.

4. A stairlift as claimed in claim 3 wherein said drive roller engages an upper one of said two spaced tubes, said biasing means including one or more biasing rollers engaging a bottom surface of said upper tube.

5. A stairlift as claimed in claim 3 wherein said drive roller engages an upper one of said two spaced tubes and said biasing means includes one or more biasing rollers engaging a lower one of said two spaced tubes.

6. A stairlift as claimed in claim 6 wherein said biasing roller defines in part said means for resisting rotation of said carriage about said length axis.

7. A stairlift as claimed in any one of claims 3 to 6 wherein said means to resist rotational movement of said carriage about said length wise axis includes a plurality of support rollers engaging a lower one of two spaced apart said tubes.

8. The stairlift as claimed in claim 7 wherein said plurality of support rollers includes two rollers engaging said down tube on opposite sides of a longitudinal centerline of said down tube.

9. The stairlift as claimed in claim 8 wherein said two rollers include a first roller rotatable about a fixed axis; and a second roller rotatably mounted on an arm, the arm being mounted for pivoting about the fixed axis.

10. A stairlift as claimed in any one of the preceding claims wherein said biasing roller is mounted and configured to apply a biasing force along spaced apart biasing axes, said biasing axes being substantially perpendicular to said length direction axis.

11. A stairlift as claimed in any one of the preceding claims wherein said drive rollers are mounted for pivoting about pivots perpendicular to said length direction axis, each of said pivots being located in a reference plane of the respective drive roller.

12. A stairlift as claimed in any one of the preceding claims wherein the contact surface of said drive roller has substantially the same shape as those portions of said rail with which it is in contact when viewed along said length axis.

13. A stairlift as claimed in any one of the preceding claims further including levelling means configured and operable to effect relative rotation between said chair and said carriage to maintain said chair substantially horizontal as said carriage moves through the curvature of said rail in a vertical plane.

14. A stairlift as claimed in any one of the preceding claims wherein said rail includes a bend having a radius substantially equal to twice the diameter of the tube forming the tail.

15. A stairlift as claimed in any one of the preceding claims wherein said drive roller has a drive surface formed of polyurethane having a shore hardness in the range 92 to 95.

16. A stairlift as claimed in any one of the preceding claims wherein said rail has an upper end and a lower end when mounted in a stairlift, the portion of the rail terminating in said lower end being substantially vertical.